The mystery about this one is that it's not a Barbara Vine. It has next to no detective element and centres on the psychosocial complications favoured by Ruth Rendell's alter ego. Sixteen-year-old Liza is given some money by her mother Eve and told to go make her way to a friend of Eve's in London, problem being that the police have just paid a call to the little guesthouse where mother and daughter have always lived, on a remote West Country estate, and Eve is liable to be booked for murder in the morning.

Liza, who has never been further than the nearest small town, ignores instructions, and runs to find Sean, the young estate gardener she's secretly been sleeping with, at his caravan. As they spend the autumn travelling around apple-picking and otherwise odd-jobbing, Liza tells Sean the story of her curious upbringing and her wonderful but just occasionally homicidal mother - now on remand, according to the papers. Uncertain how shocked he is going to be, she breaks it to him an episode at a time, 'like Sheherezade', she says. 'She-who?' says Sean.

Rendell fills us in on the same pattern, dialogue revelations in the caravan leading to old-fashioned flashback narrative. It is a very mechanical and artificial method of proceeding, often used by hack authors because of its possibilities for the calculated management of tension and often unsuccessful because of its formal obviousness. Still, Homer did something like it; and Rendell, though a bewilderingly prolific writer with a chokehold on station and airport bookstalls so lucrative that she is now a corporation for tax purposes, clearly counts as more than a hack. Despite our awareness of the creaky old ploy she makes it work like a charm.

The situation between teller and listener, Liza and Sean, really does call for a careful bit-by-bit approach. Liza, given an illegal but rigorous classical education by Eve, has never been to school or had any friends. Her TV-watching, all in the usually unoccupied big house on the estate, has been covert and patchy because Eve implicitly banned TV by omitting to mention its existence.

She has never been told who her father was, though she has her suspicions, which turn out to be dramatically off the mark. Her real name is Eliza and she wonders if Eve was thinking of Eliza Doolittle in Pygmalion. 'Come again?' says Sean. She explains. 'Sounds like My Fair Lady to me,' he says. She's never heard of that.

Eve's project was to make Eliza like herself as she 'should have been' but for an upset which she never mentioned and which Liza only discovers when the papers cover the trial. Eve's misdeeds anchor the structure but the book works as Bildungsroman rather than thriller, the fascination lying in the growth of Liza's mind under these unusual conditions. Since things are seen through a child's eyes we have the estate owner's corduroy trousers described as 'fawn stuff like the ribbing on a jumper' and a record noted as 'something called Mozart'. Talking to the reader over the character's head like this can become arch and faux-naif, and it does, but not to a ruinous extent. Rendell has a safe pair of craftsmanlike hands.

The Sheherezade motif hints ironically that here the listener may be in danger from the teller rather than the other way round. A specious way to crank up some ordinary plotty tension, it also contains something cleverer, a gradual intimation that even if this strange and appealing Liza were to go wrong in a murderous direction like her mother, we would still be in helpless sympathy with her. After which realisation it hardly matters in literary terms whether she does or not.

Rendell is not always this good: her last outing as Barbara Vine, King Solomon's Carpet, achieved an unintentional hilariousness with its catalogue of doom in West Hampstead, and she still shows scant sign of the sense of humour that novelists strictly need. The dialogue I've quoted is about the limit of it. Even so, The Crocodile Bird (Eliza pictures her mother and herself in symbiosis like the croc and the little bird it permits to pick its teeth unharmed) is a strong performance that should spoil the trains-and-planes readership rotten.